PPA description

Ubuntu Oneiric (11.10) systems already include all the kernel and gnome-settings-daemon fixes (this PPA is not needed for Oneiric systems). However, some Oneiric users may still need to add the boot parameter "acpi_backlight=vendor" (see details delow).

This PPA is ONLY relevant to Ubuntu Maverick/Natty with the Gnome or Unity desktops (KDE desktop see below). The functionality it provides is not available for previous Ubuntu versions.

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BEFORE YOU INSTALL, CHECK FOR THE i915 DRIVER ON YOUR SYSTEM:

This patch requires an Intel graphics processor (i915-based) to operate (*or possibly Radeon, see below). Verify that your system uses the i915 driver:

$ lsmod | grep ^i915
i915 331519 3 <--- an "i915" line should appear

If no "i915" line appears, then this PPA will not be useful on your system.

NOTES FOR RADEON USERS

This patch might also fix backlight brightness control for systems with Radeon graphics processors by enabling a new interface: sys/class/backlight/radeon_bl . This Radeon support has NOT been tested; feedback will be appreciated.

NOTES FOR KDE DESKTOP USERS

KDE desktop users: This PPA may NOT fix your backlight control hotkeys: This fix requires a kernel module to supply the new /sys/class/backlight/intel_backlight interface (which will work regardless of your desktop) and also a desktop module to access that interface. For Gnome, the updated gnome-power-manager in this PPA supplies that, but the equivalent for KDE has not yet been developed.

Applying this PPA will:
1. update the linux kernel to add a new backlight control interface: /sys/class/backlight/intel_backlight
2. update the gnome-power-manager to bind the brightness up/down keys to intel_backlight in preference to other backlight control interfaces in /sys/class/backlight.

If applying this PPA still doesn't enable your non-functional brightness control keys, check your backlight interfaces to verify that the new "intel_backlight" interface appears:

$ ls /sys/class/backlight

For some laptop models, it may also be necessary to manually disable the other backlight interfaces in /sys/class/backlight. The following kernel boot parameters can be used to disable other backlight interfaces. Instructions for using kernel boot parameters are available at https://wiki.ubuntu.com/Kernel/KernelBootParameters .

Finally, if "intel_backlight" is the only interface that appears in /sys/class/backlight but the brightness control keys still do not work, you may wish to troubleshoot further using the methods described at https://wiki.ubuntu.com/Hotkeys/Troubleshooting .

Additional kernel boot parameters (should not normally be needed):

acpi_backlight=vendor
The boot parameter acpi_backlight is now set to "=vendor" internally in kamal~mjgbacklight kernels (there is no need to specify this parameter). This disables the /sys/class/backlight/acpi_video0 backlight interface to preclude interference with intel_backlight.

i915.asle_backlight (relates to Maverick (mjgbacklight4) version only! default =0)
By default, the internal routine asle_set_backlight is disabled in kamal~mjgbacklight4 kernels as it was observed to interfere with intel_backlight on some systems. The boot parameter i915.alse_backlight=1 can be set to re-enable it for experimental purposes.

SOURCE PATCHES / GIT BRANCHES:

The sources for the kamal~mjgbacklight kernels (the patch sets for Ubuntu kernels) are available here in the following git branches. The ported patches are those above the one marked "UBUNTU: Ubuntu-2.6.xx-yy.zz".